Dear All. I encountered a compatibility problem when reimplementing the enc28j60 controller that depends on the modified SPI API (that is planned to be a future feature to be added to the Arduino project). The problem concretely is that the previous implementation of the enc28j60 interface completely depends on the "command + data" spi interface. That is incompatible with the new SPI API, that is designed for "only data" interface. Then, I foresee two design possibilities. (1) Modify the SPI API to include one more "transfer" overloading that handles sending one byte and immediately after a buffer. There are multiple possibilities for implementing this. The first one that pops to my mind is to implement the only buffer case as a sub-case of the command one, and give the buffer first value as command. (2) Reimplement the Enc28j60 interface to generate "only buffer" calls to the SPI API by inserting the command as the first element of the buffer and the real buffer from the second place and ahead, increasing the length of the current buffers by one. After some thinking, I am leaning toward the second, as the new CoAP implementation already allows the feature to pass the buffer pointer as function parameter at different positions of the buffer. Passing the buffer through the stack already relies on this characteristic. Then, the modification needed is to increase the size of the buffer by one, to allow inserting the command at the very beginning of the buffer. But I am not sure if it is the optimal decision, or there exist maybe another option that I could not see right now. Please, discuss and comment as required. With Warm Regards, Ivan Raul